Fire fighters, emergency service vehicles and a helicopter in Moskovsky Prospekt at the entrance to Tekhnologichesky Institut station of the St Petersburg metro in the aftermath of an explosion which occurred in a train at 14:40 Moscow timeon April 3, 2017. (Photo by Peter Kovalev/TASS)

People spray water in the street ahead of “Songkran”, the annual Thai New Year water-throwing festival, in Kowloon City, Hong Kong, China, 09 April 2017. The pouring of water is a key element in the festival as it represents purification and the washing away of one's sins and bad luck for the year. The event also includes a “Miss Songkran” pageant where contestants are clothed in traditional Thai dress, and a winner is crowned. This year's “Songkran” will begin in Thailand on 13 April 2017. (Photo by Alex Hofford/EPA)

A man wearing an illuminated atmospheric diving suit as part of an installation titled “What Lies Beneath” looks at members of the public during the Vivid Sydney festival of light and sound in Sydney, Australia, May 26, 2017. (Photo by Steven Saphore/Reuters)

Cosplay fans (R) take selfies as comic book and gaming fans attend the annual Ani-Com and Games Fair in Hong Kong on July 28, 2017. Tens of thousands were expected to attend the annual event on animation, comics and games, from July 28 to August 1. (Photo by Isaac Lawrence/AFP Photo)

A general view shows the wreckage of armed trucks on the streets of Budapest at the time of the uprising against the Soviet-supported Hungarian communist regime in 1956. The picture was taken in the period between October 23 and November 4, 1956. (Photo by Laszlo Almasi/Reuters)

Women hold a demonstration on Backwater Bridge during a protest against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, U.S. November 27, 2016. (Photo by Stephanie Keith/Reuters)

A woman walks up the steps decorated ahead of the Chinese New Year festival in Beijing, China, Thursday, January 12, 2017. The Chinese Lunar New Year is the most important holiday for Chinese and hundreds of millions are expected to return to their hometown to spend the new year with their family and relatives. (Photo by Ng Han Guan/AP Photo)

Indian men stand around sword fish for sale at a harbour a harbour in Chennai on June 5, 2016, as fishermen return with their catch after a 45-day fishing ban on the east coast of India. Authorities in the southern Indian state of Tamil Nadu had imposed a 45-day ban on fishing by mechanised vessels to protect marine life, with only “country boats” operating within five nautical miles off the coast. (Photo by Arun Sankar/AFP Photo)